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MG Car Repair/MGTF differential noise


Hello Barrie,
I have a 54 TF 1250 (Australia)and I recently put new bearings in the differential (4.875) because of noise on the overrun.
It turned out that there were shims in the pinion spacer. One had had collapsed and another very nearly so.  I think the diff had been like this for many years and I had put up with it. I had 85/140 oil in it for the last few years.
I have now replaced all the diff (and wheel) bearings. I am confident that the pinion pre-load is correct (about 10-11 inlb)as near as I could measure. The carrier spacers were reinserted as they had been on disassembly.I have done about 50 miles and the diff whines on light load - not on deceleration or acceleration. It is more pronounced when the new oil(85/90)gets warm. I have assumed that because the pinion had slopped back and forth (maybe 6-8 thou.)for many years and is now locked in position, that the mating surfaces are now different causing the whine, and that it will eventually go away!!
The pinion washer is the same as before and the crown wheel and pinion were judged by others to be free of chips, marks etc. The "lipstick" test showed the mating surfaces were about right.
I have just changed the oil (85/90)and there were a very few small particles of metal in the replaced oil(85/90). I am loath to put 85/140 oil back in because the new roller bearings might not get sufficient lubrication with the higher viscosity oil.
Is it wishful thinking that the noise will go away? What else can I do?
Kind regards,
David Taylor (Hobart, Tasmania)

Hi David

You have a 60 year old Crownwheel & Pinion which has been running for some time in a misaligned state due to collapsed shims.  This will have polished the wrong part of the mating surfaces, whilst the 'correct' part will not have been polished in places and may have even developed a slight ridge.  Now (hopefully) the pinion is correctly aligned and it has the job of polishing the parts that were previously missed.  

I would live with the slight whine and use the car.  It will take at least a thousand miles before you can judge whether the noise is diminishing or not.  Do not be tempted to change the oil again until you have done at least 6,000 miles.  This will only slow down the polishing process.  

Let me know how you get on.

Yours Octagonally,

ps - please send me a reply including your TF chassis number  

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Barrie Jones


MG Sports Cars from 1949 to 1980 - Including MGB, MGBGT V8, TF1500, TF, TD and modern Midgets. I also specialise in SU carburettors, Lucas wiring, suspension, steering & brakes.


I have owned my 1955 TF1500 since 1966. Technical specialist for the TD and TF with the MG Car Club T Register. Also owned 20 MGBs and currently own an MGBGT V8. Written 3 books on MGs and produced a DVD on how to strip and rebuild the TD/TF gearbox.

MG Car Club.

Barrie's Notes on the 1953-55 MG TF (author). /=====/ Barrie's Notes on the MGB (author). /=====/ Barrie's Notes on the MGB GT V8 (author). /=====/ The Essential Buyer's Guide to the MG TD, TF and TF1500. (author)

M Phil, C Eng, BSc (Eng).

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